Let us know the results of printing using WePrint so we can help you further. Also make sure you have "WePrint:" showing in the Server field on the Print screen for this test, or tap on the Choose button to select it.
Is "WePrint:" showing in the "Server" field on the Print screen in the iPhone/iPad App? If not, tap the "Choose" button beside the printer field. In the next "Printers" screen, tap on the "All" tab. If WePrint isn't found automatically, tap on the "+" button in the top right and enter your WePrint address and tap "Connect" in the "Add Printer" screen.
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This page will describe how to print email.